- Synthesis of Arylamides via Ritter-Type Cleavage of Solid-Supported Aryltriazenes
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A novel route for the synthesis of N-arylamides via the cleavage of aryltriazenes with alkyl or aryl nitriles is presented. We developed a variation of the Ritter reaction that allows the use of acetonitrile as solvent and reagent in reactions with solid-supported precursors. The reaction was optimized for the generation of N-aryl acetamides using a diverse range of immobilized building blocks including o-, m-, and p-substituted aryltriazenes. The cleavage via the Ritter-type conversion was combined with an on-bead cross-coupling reaction of halogen-substituted aryltriazenes with pyrazoles. Additionally, the synthesis of on-bead generated arylboronic ester-substituted triazenes was shown. The developed procedure was further expanded to use other commercially available nitriles, such as acrylonitrile, benzonitrile, and chlorinated alkyl nitriles as suitable reagents for a Ritter-type cleavage of the prepared triazene linkers.
- Wippert, Nicolai A.,Jung, Nicole,Br?se, Stefan
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supporting information
p. 568 - 572
(2019/09/03)
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- The oxidative bromination and iodination of dimethylacetanilides
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The oxidative bromination and iodination of the six dimethylacetanilides have been examined; whereas bromination of 2,4-dimethyl- and 2,6-dimethylacetanilides using potassium bromide, sodium tungstate and peracetic acid gave predominantly the 6- and 4-bro
- Medina, Inmaculada C. Rodriguez,Hanson, James R.
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p. 428 - 429
(2007/10/03)
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- Oxidative Bromination of Aromatic Amides using Sodium Perborate as Oxidant
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Sodium perborate in glacial acetic acid-acetic anhydride with potassium bromide and sodium tungstate as a catalyst, provides a novel system for the bromination of aromatic amides.
- Hanson, James R.,Harpel, Simone,Medina, Inmaculada C. Rodriguez,Rose, Dorian
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p. 432 - 433
(2007/10/03)
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- Nature of nitrenium: carboxylate ion pair intermediates in the hydrolysis of O-aroyl-N-acetyl-N-(2,6-dimethylphenyl)hydroxylamines
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O-Aroyl-N-acetyl-N-(2,6-dimethylphenyl)hydroxylamines are solvolysed in aqueous solutions by rate-limiting ionization to nitrenium:carboxylate ion pair intermediates.These in part collapse at the ortho position to give unstable 1,5-dimethyl-5-aroyloxy-6-acetyliminocyclohexa-1,3-dienes 2 that react further as described in the previous paper.The ion pairs from 1 also proceed directly to products of substitution para to the acetylamino group - 4-aroyloxy-2,6-dimethylacetanilide 5, a product of internal return, and 4-hydroxy-2,6-dimethylacetanilide 6, a product of water addition.These same products also arise via ionization of 2.The ratio 5:6 obtained directly from 1 is significantly lower than that from 2, demonstrating that 1 and 2 do not ionize to exactly the same ion pairs.Experiments with 1a in the presence of bromide show that the yield of the cyclohexadiene is unaffected, while the yields of 5 and 6 are decreased, albeit to different amounts.Two new products, 4-bromo-2,6-dimethylacetanilide and 2,5-dimethylacetanilide, are observed in their places.Experiments with 1c in acid solutions demonstrate that the yield of cyclohexadiene can be decreased by H+, by protonation of the carboxylate ion in the ion pair.Using the H+ reaction as a clock, the lifetime of this ion pair, the initial ion pair in the ionization of 1, is calculated as ca. 10 ps.Thus this ion pair is too short-lived to react with external nucleophiles, and probably also with solvent.The trapping data for the p-ester 5 are shown to be inconsistent with a mechanism where a single ion pair serves as precursor, and this product is proposed to arise in part from a short-lived ion pair, and in part from a longer-lived one.The latter ion pair is probably also the species that gives rise to the p-phenol 6 by reaction with water.Using the bromide reaction as the clock, this ion pair is shown to have a lifetime of 0.25-0.50 ns.A number of mechanistic models incorporating these features are consistent with the experimental results, and two of these are discussed.Whatever the mechanism a minimum of three short-lived ion pair intermediates is required.
- Fishbein, James C.,McClelland, Robert A.
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p. 663 - 672
(2007/10/02)
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